The study, led by Philipp Radler in the laboratory of Christa Schleper at the University of Vienna and published in the journal Nature, provides the first direct observations of Asgard archaeal motility. These organisms are tiny; each cell has a volume roughly a thousand times smaller than that of a human cell. Yet the recordings show them undergoing dramatic transformations of shape on a minute-by-minute basis, extending thin appendages that can reach up to twenty times the length of the cell body, retracting them again, and using them to actively explore their surroundings. The behavior is strikingly reminiscent of the amoeboid movement seen in far more sophisticated cells, including human immune cells patrolling tissue.

Why does this matter so much? Asgard archaea occupy a central position in current models of eukaryogenesis, the process by which the first complex cells emerged roughly two billion years ago. The prevailing scientific framework holds that a eukaryotic ancestor arose from a symbiotic fusion between a bacterium and an archaeal lineage ancestral to today’s Asgard archaea. In that scenario, the bacterium eventually became the mitochondrion, the energy-producing organelle that powers virtually every complex cell on Earth. Asgard archaea are therefore not merely an interesting branch of the microbial tree; they are the closest available window into the cellular world from which our own lineage was born.

Until very recently, that window was almost entirely opaque. The first Asgard archaea were only brought into culture in 2020 and 2023, one at the JAMSTEC Institute in Japan and another in Schleper’s laboratory in Vienna, and both Japanese teams are co-authors on the new study. Before those milestones, essentially everything scientists knew about the group came from DNA sequencing of environmental samples or from electron microscopy of fixed cells. Those static images were already tantalizing: they showed a round cell body surrounded by a halo of fine, branching projections. But a fixed image cannot reveal whether a cell is extending, retracting, or moving, and so the functional significance of these elaborate shapes remained a matter of speculation.

The Vienna team closed that gap with a technically demanding approach. Asgard archaea are anaerobes, organisms that cannot tolerate oxygen, so the researchers placed the cells in an oxygen-free environment and filmed them alive under the microscope. They worked with two strains: a Lokiarchaeon cultivated in Vienna and a Heimdallarchaeon cultivated in Japan. Both organisms displayed the same remarkable repertoire of behaviors, drastically reshaping themselves every minute and deploying their thin, dynamic appendages to attach to surfaces and probe them. The crawling motion they use had not previously been described in any microbe, and its closest parallels lie in the motility of complex eukaryotic cells.

The mechanistic story behind the movement is equally significant. When the team applied actin inhibitors to the cultures, the dynamic behaviors were suppressed. Actin is one of the fundamental components of the cytoskeleton, the internal scaffolding that gives cells their shape, drives their internal transport, and powers their movement. In eukaryotes, an actin-based cytoskeleton underlies everything from muscle contraction to the crawling of immune cells through tissue. Finding that the motility of Asgard archaea likewise depends on actin suggests that a functional actin cytoskeleton, with clear parallels to the one operating in human cells, was already in place in the archaeal lineage long before the first eukaryote existed.

The international collaboration behind the study included, alongside the Japanese microbiologists, researchers from the Institute of Science and Technology Austria and the Helmholtz Centre for Infection Research in Braunschweig, Germany. Their combined expertise in cultivation, microscopy and cell biology was essential to a result that no single laboratory could have achieved alone. Culturing Asgard archaea remains extraordinarily difficult; the organisms grow slowly, in strict anaerobic conditions, and only a handful of laboratories worldwide have managed it. Every live-cell observation therefore represents years of methodological groundwork.

From an evolutionary standpoint, the discovery opens a genuinely new perspective on the deep history of cellular innovation. Complex cell motility may have far older origins than previously assumed, predating the emergence of eukaryotes themselves. If the ancestor of Asgard archaea already possessed the machinery for shape change, surface attachment and crawling, then some of the cellular capabilities once thought to be eukaryotic inventions may instead have been inherited from their archaeal partner. Such capabilities could even have played a role in the ancient symbiosis from which mitochondria later emerged, potentially facilitating the physical interactions between the archaeal host and its bacterial partner that set complex life in motion.

The findings also carry practical implications that extend well beyond evolutionary theory. Because the actin cytoskeleton governs shape changes and motility in human cells, understanding a simpler, archaeal version of the same machinery offers a comparative framework for dissecting how this fundamental system works. Insights gained from organisms that sit at the evolutionary boundary between prokaryotes and eukaryotes can illuminate which features of the eukaryotic cytoskeleton are ancient inheritances and which are later refinements. In this sense, the humble Asgard archaea, invisible to the naked eye and difficult to culture, may help explain processes that are central to human biology, including immune cell migration and cellular architecture.

Perhaps the most consequential aspect of the study is methodological. Oxygen-free live-cell microscopy of Asgard archaea now makes it possible, for the first time, to test models of the origin of complex life against empirical observation rather than inference from genomes and static images. Hypotheses about how the first eukaryotes moved, attached to surfaces, and interacted with partner cells can now be confronted with real footage of their closest living relatives in action. What has emerged from those first recordings, dynamic protrusions, actin-dependent crawling and a fluidity of form once thought to belong exclusively to complex cells, suggests that the road to eukaryotic life may have been paved with cellular behaviors far older and far more sophisticated than anyone had imagined.

Subject of Research: Crawling motility and actin-based cytoskeleton dynamics in Asgard archaea and their implications for eukaryogenesis

Article Title: Unexpected dynamics of ancient microbes discovered

Article References: Unexpected dynamics of ancient microbes discovered. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Asgard archaea, Lokiarchaeon, Heimdallarchaeon, eukaryogenesis, actin cytoskeleton, cell motility, crawling motility, live-cell microscopy, mitochondria, evolution, University of Vienna, Nature

Anaerobic microbes, by nature, inhabit niches where oxygen is absent or present only in trace amounts. Many of these organisms cannot tolerate oxygen exposure, which has led to substantial challenges in studying their physiology, ecology, and interactions within microbial consortia. Over the last two decades, molecular tools like next-generation sequencing (NGS) have become indispensable for profiling these communities. High-throughput sequencing enables researchers to identify microbial taxa and infer functional potential, even when cultivation is impossible. Yet, this genomic information alone is insufficient to fully unravel the complexities of microbial function, metabolic pathways, and interspecies relationships that define microbial ecosystems.

Cultivation of anaerobic microbes, therefore, remains the cornerstone for comprehensive microbiome research. Isolating strains in pure culture allows scientists to delve into the biochemical and genetic underpinnings that govern microbial behavior. These isolates serve as model organisms to experimentally validate findings generated through ‘omics’ data, making possible the discovery of novel enzymes, metabolic pathways, and mechanisms of microbe–microbe and microbe–host interactions. Furthermore, cultured anaerobic microbes are invaluable for translational applications in biotechnology and medicine, including the development of probiotics, bioremediation strategies, and the harnessing of microbes for sustainable bioenergy production.

The past decades have seen incremental advances in anaerobic cultivation methods, ranging from the use of custom-built anaerobic chambers and sophisticated media formulations to the application of co-culture techniques. Despite these innovations, many anaerobic microbes remain uncultivated, creating a formidable “microbial dark matter” that conceals vast biodiversity and unexplored functions. Pioneering new approaches in biotechnology are now being leveraged to overcome these limitations. These include automated cultivation platforms that can precisely control anaerobic conditions, microfluidics for high-throughput isolation and screening, and innovative culture media designed to mimic natural microbial habitats more closely.

A key bottleneck in cultivating anaerobic microbes is maintaining stringent anoxic conditions throughout the isolation and growth processes. Oxygen is toxic to many obligate anaerobes due to their lack of protective enzymes like catalases and superoxide dismutases, which detoxify reactive oxygen species. Advances in inert gas atmospheres, oxygen scavengers, and rapid transfer systems have improved anaerobic handling, but the development of next-generation anaerobic workstations integrating automation, real-time monitoring, and parallel cultivation capacity promises to revolutionize throughput and reproducibility in cultivation workflows.

Beyond hardware innovations, conceptual shifts in cultivation strategies are underway. Traditional efforts often attempted to mimic broad environmental conditions, inadvertently excluding key symbiotic or syntrophic relationships required for growth. Emerging techniques emphasize co-cultivation and consortia assembly, recognizing that many anaerobes depend on close metabolic interactions with partner microbes for essential growth factors or electron donors and acceptors. By recreating these interdependencies, researchers can cultivate previously elusive species, thereby expanding the known microbial repertoire.

The promise of enhanced anaerobic cultivation extends into unraveling the biochemical mechanisms that govern microbial interactions and host associations. For example, in human health, anaerobic microbes dominate the gut and influence numerous physiological processes, including immune modulation, nutrient metabolism, and pathogen resistance. Cultivation allows detailed functional assays, genetic manipulation, and phenotypic characterization, enabling the translation of microbiome science into clinical interventions such as targeted microbial therapies and diagnostics.

In environmental contexts, cultivated anaerobic microorganisms contribute to ecosystem functions like nutrient cycling, organic matter degradation, and greenhouse gas emissions. Understanding their metabolic pathways through isolates leads to improved models of biogeochemical processes and informs strategies for mitigating climate change impacts, such as enhancing methane capture or reducing nitrous oxide emissions. Moreover, cultured anaerobic microbes have applications in industrial biotechnology for processes like anaerobic digestion, biogas production, and synthesis of bio-based chemicals, which are critical for sustainable development.

However, the path to achieving methodical, high-resolution anaerobic cultivation is fraught with technical and infrastructural challenges. Key obstacles include the need for specialized training, high operational costs, limited access to state-of-the-art anaerobic facilities, and a scarcity of standardized protocols across laboratories. Addressing these issues requires coordinated efforts to democratize anaerobic cultivation technologies through open-source designs, modular instrumentation, and collaborative networks that facilitate knowledge sharing and data integration.

Looking ahead, the integration of cultivation with multi-omics approaches and computational modeling heralds a new era in microbiome research. Cultivated isolates provide invaluable ‘ground truth’ for interpreting metagenomic, metatranscriptomic, and metabolomic datasets, while advanced bioinformatics can guide cultivation by predicting optimal growth conditions based on genomic signatures. Leveraging artificial intelligence and machine learning to analyze vast data streams will optimize strain selection and medium formulation, thereby accelerating the discovery pipeline.

Importantly, next-generation anaerobic cultivation is not an incremental step but a paradigm shift that elevates microbiome science from descriptive cataloging to functional elucidation. This shift unlocks the potential to design synthetic microbial communities with desired functionalities, engineer microbial consortia for therapeutic and environmental applications, and uncover fundamental principles of microbial ecology and evolution. As a result, we can anticipate profound impacts across health, agriculture, industry, and environmental stewardship.

Several pioneering laboratories are spearheading this frontier by developing integrated anaerobic cultivation platforms combining robotics, microfluidics, and high-throughput analytics. These technologies enable the screening of thousands of microbial isolates concurrently, identifying novel organisms and metabolic capabilities with unprecedented speed and precision. The deployment of these platforms will likely stimulate a renaissance in exploring microbial diversity and function, catalyzing discoveries that were previously unimaginable.

Furthermore, the ethical and regulatory landscape surrounding microbial cultivation and application is evolving alongside technological advancements. Responsible stewardship is essential to ensure that cultivated microbes, particularly genetically modified strains or those introduced into human or environmental settings, comply with safety and environmental standards. Transparent communication and collaborative governance will support the sustainable and equitable development of anaerobic microbiology.

In conclusion, the surge in biotechnological innovations aimed at enabling next-generation anaerobic cultivation marks a critical juncture in microbiome research. The capacity to culture and study anaerobic microbes in controlled environments unlocks a treasure trove of biological knowledge and practical applications. This transformation will deepen our understanding of microbial life’s hidden facets, inspire novel therapeutic and industrial strategies, and ultimately redefine the boundaries of microbiome science in the 21st century and beyond. The convergence of cultivation, sequencing, and computational tools promises an exciting future where the mysteries of anaerobic microbial communities are finally brought to light.

Subject of Research: Anaerobic microbial cultivation and its role in advancing functional microbiome research.

Article Title: Enabling next-generation anaerobic cultivation through biotechnology to advance functional microbiome research.

Article References:
Clavel, T., Faber, F., Groussin, M. et al. Enabling next-generation anaerobic cultivation through biotechnology to advance functional microbiome research. Nat Biotechnol (2025). https://doi.org/10.1038/s41587-025-02660-6

Image Credits: AI Generated